1. Technical Field
The present invention relates to a developing unit of a multi-color image forming device, such as a color printer or a color copier, and more particularly to a developing unit of a multi-color image forming device and a controlling method thereof. The device and method provide the developing unit of the multi-color image forming device with a transporting unit for transporting a developer of the developing unit. The device and method also prevent vibration caused by the rotation of the developer and a photosensitive body by controlling the developer transporting unit, and remove the variation of the interval between the developer and the photosensitive body in the case of transfer.
2. Related Art
A multi-color image forming device comprises a printer, a copier or a scanner which can print an image composed of various colors (i.e., multi-colors) on a recordable medium. The multi-color image forming device includes: a paper feeding unit for feeding paper inside a case having a predetermined size; a charge unit for charging a transfer drum to adhere the fed paper to the transfer drum; a print unit which prints a predetermined image on the paper which is rotated as it adheres to the transfer drum, and which includes an exposing unit, a photosensitive drum and the developing unit; and a discharge unit for discharging the paper on which the printing operation is completed.
Typically, the developing unit has a plurality of developing rollers for spreading out the developing agent on an electrostatic latent image formed on the photosensitive drum. Moreover, in the developing unit, there are typically four developers corresponding to the four colors of developing agents employed. Typically, one of two types of arrangements for developing the developing agent are employed: a fixed type or a rotatable type. As stated in more detail below, the fixed type developing unit is burdened by the disadvantage that the cost of manufacturing the photosensitive drum (which must be quite large) is very high, and it is impossible to miniaturize the device. Therefore, the rotatable type developing unit is predominantly used.
However, the rotatable type developing unit is also burdened by the disadvantages. Specifically, as stated in more detail below, it has several problems since the developing roller is separated from the photosensitive drum by only a minute space, and since the turret employed therein is rotated by a mechanical driving device such as a motor.
Therefore, there is a need for the development of a developing unit and control method thereof which will effectively cope with the difference in the diameters of the developing rollers, and which will prevent the variation of space between the developing roller and the photosensitive drum when mechanical vibration of the turret occurs.
The following patents are considered to be representative of the prior art, and are burdened by the disadvantages set forth herein: U.S. Pat. No. 5,761,576 to Sugihara, entitled Image Forming Apparatus For Supplying Power To Members Of A Rotary Developing Device, U.S. Pat. No. 5,671,470 to Maruta et al., entitled Color Image Forming Device Which Changes Developing Bias When Switching Between Developer Units, U.S. Pat. No. 5,640,654 to Yoshizawa, entitled Color Image Forming Apparatus Having Rotary Developing Device, U.S. Pat. No. 5,610,701 to Terada et al., entitled Color Electrophotographic Apparatus And Image Forming Units Used Therein, U.S. Pat. No. 5,600,431 to Takeda et al., entitled Image Forming Apparatus For Forming Color Image With Dry Developer, U.S. Pat. No. 5,585,598 to Kasahara et al., entitled Rotary Developing Device For An Image Forming Apparatus, U.S. Pat. No. 5,552,877 to Ishikawa et al., entitled Image Forming Apparatus With Controlled Drive For Accurately Positioning Developing Sections of A Rotary Developing Device, U.S. Pat. No. 5,486,902 to Ito, entitled Color Image Forming Apparatus For Forming Color Image By Transferring Color Toner To Transfer Material, U.S. Pat. No. 5,758,235 to Kosuge et al., entitled Toner Container For A Rotary Developing Device, U.S. Pat. No. 5,440,373 to Deki et al., entitled Color Image Forming Apparatus, U.S. Pat. No. 5,724,634 to Maruta, entitled Image Forming Device In Which Developer Roller Speed Is Controlled In Developer Transfer To A Photoconductive Drum, and U.S. Pat. No. 5,752,141 to Nishimura et al, entitled Rotating Type Developing Apparatus.